Dissociated Recombinant Human Bone Morphogenetic Protein-2 (rhBMP-2) Retains Osteoinductive Potential: An In Vivo...

Area of Science:

• Biomaterials Science
• Regenerative Medicine
• Orthopedic Surgery

Background:

• Recombinant human bone morphogenetic protein-2 (rhBMP-2) is a potent osteoinductive factor used in bone regeneration.
• The delivery scaffold, such as absorbable collagen sponge (ACS), influences rhBMP-2 release and efficacy.
• Understanding rhBMP-2 behavior after dissociation from its carrier is crucial for assessing clinical risks.

Purpose of the Study:

• To investigate the osteoinductive capacity of rhBMP-2 after dissociation from its ACS carrier.
• To evaluate ectopic bone formation induced by soluble rhBMP-2 transported via supernatant run-off (SRO).
• To assess the potential clinical relevance of off-target mineralization by liberated rhBMP-2.

Main Methods:

• rhBMP-2 loaded ACS was centrifuged to collect SRO containing dissociated rhBMP-2.
• rhBMP-2 concentration in SRO was quantified using UV spectrophotometry.
• ACS and SRO were implanted/injected into athymic nude rats, followed by micro-CT and histological analysis at 28 days.

Main Results:

• Centrifugation released approximately 11.3% of rhBMP-2 into the SRO.
• Both ACS and SRO induced mineralized tissue formation in vivo.
• SRO resulted in significantly lower total tissue volume compared to ACS, but similar bone volume fraction and bone mineral density.
• Histology showed variable mineralization in SRO, ranging from cartilage to woven bone, while ACS showed more consistent but heterogeneous bone formation.

Conclusions:

• Dissociated rhBMP-2 retains osteoinductive potential and can induce ectopic mineralized tissue.
• The findings suggest a conservative estimate of clinical risk, as clinical burst release exceeds the tested concentration.
• Liberated rhBMP-2 may contribute to off-target mineralization, emphasizing the need for improved controlled-release strategies.